Pardo took a feed from forward Doninic Oduro on the goal line, and beat goalkeeper Faryd Mondragon with a 17-yard kick about nine minutes into the second half.
The score erased Philadelphia's lead, which had been achieved on Veljko Paunovic's 30-yard shot in the 34th minute. The left-footed shot went low past goalkeeper Sean Johnson, who was screened by Chicago defender Josip Mikulic.
The point moved Philadelphia with in two points of Eastern Conference leader Columbus. The tie broke Chicago's two-game losing streak, and was its fifth deadlock in seven games.
The 35-year-old Pardo was signed on July 26, and wasn't expected to play for more than a half in his Chicago debut. Instead, the Mexican League veteran settled the Fire's defensive play in midfield, and made the game's biggest offensive play.
It was the Union's first match since the team announced leading scorer Carlos Ruiz was being released. Ruiz signed a contract with Veracruz of the Mexican League on Wednesday.
Philadelphia head coach Peter Nowak missed the match because of severe back spasms. Assistant John Hackworth ran the team in Nowak's absence.
(Copyright 2011 Philadelphia Union. Reprinted by permission)